Repetitive scanning of a record track on a fragment of a record



Jan. 22, 1963 s. GORDON ETAL RERETITIVE SCANNINC oF A RECORD TRACK oN A FRACMENT oF A RECORD 5 Sheets-Sheet 1 Filed Sept. 10, 1958 QQ QQ Www NQ NNN Jan. 22, 1963 s. GORDON ETAL 3,075,049

REPETITIVE scANNING oF A RECORD TRACK oN A FRAGMENT oF A RECORD Filed Sept. l0, 1958 5 Sheets-Sheet 2 Jan. 22,- 1963 s. GoRDoN ETAL x 3,075,049

REPETITIVE SCANNING OF A RECORD TRACK oN A FRAGMENT oF A RECORD Filed Sept. l0, 1958 5 Sheets-Sheet 3 Tlf ""1 .p q

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ATTORNEYS Jan. 22, 1963 s. GoRDoN ETAL 3,075,049

. REPETITIVE scANNING oF A RECORD TRACK 0N A FRAGMENT oF A RECORD Filed sept. 1o, 1958 5 sheets-sheet 4 IN ENTORS Mann .JSM/Ps. ff/MME? GORDd/V misc-ww Jan. 22,1963 s. GORDON ETAL 3,075,049

RERETITIVE sCANNINC. oF A RECORD TRACK oN A FRAGMENT oF A RECORD Filed Sept. 10, 1958 5 Sheets-Sheet 5 LAMA, i

,4770 /VEys ilnited States Patent O REPETITIVE SCANNING GF A RECRD TRACK N A FRAGIVIEN'I 0F A RECRI) Sumner Gordon, New London, and William F. Saars,

Niantic, Conn., assignors to The United States of America as represented by the Secretary of the Navy Filed Sept. 10, 1958, Ser. No. 760,274 4 Claims. (Cl. 179--10il.2) (Granted under Title 35, U.S. Code (1952), sec. 256) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to repetitive scanning of 'a selected record track along a fragment of ya record medium where the selected record track does not close on itself, and where the fragment having the selected record track is not physically dissociated from the remainder of the record medium. More particularly, this invention relates to examination in detail of signal `data recorded on sections of an elongate record medium such as magnetic tape without cutting the tape to isolate the tape sections of interest.

It is common practice at the present time to record signals emanating from various sources to enable scrutiny and detailed examination of the signals at a conveniently selected time and under selected conditions. Heart sounds, radar and sonar echoes, oil exploration echoes, radio signals from space, ygeophysical mapping pulse echoes, iish and bat signals are examples of the variety of signals that are recorded for detailed study. Magnetic tape and wire recorders are commonly used for recording such signals but there are other types of recorders current available and which can record such signals; they record on disks, drums or belts and operate on magnetic, electrostatic, or modulated groove principles. Regardless of the type of recorder used, the signal is recorded along a continuous record track on the record medium. Recorded signals are reproduced from the record with the aid of suitable playback equipment by placing the sensing head of the playback equipment in sensing relation with the record track and moving the record and the sensing head relative to each other so that the sensing head traverses the record path. The sensing head generally can -be brought into engagement with the record manually at any point along the record track and can be disengaged from the record track further along whereby it is a simple matter to play back a desired fragment of the record only. By marking points along the record track corresponding to the ends of the selected fragment, that fragment can be played back repeatedly by repeating the engaging and 4disengaging steps. By this method, a particular signal recorded on a fragment of `a record can be observed over and over lagain at intervals with the aid of an oscilloscope or listened to over and over again with the aid of audio equipment.

Where the signal of interest has an irregular or complex waveform, it is not usually possible to analyze the signal if it is observed only transitorily at spaced intervals of time, as above, regardless of the number of times it is observed. It is necessary to present the signal waveform so that is is stationary on an oscilloscope screen, or properly continuous and of proper bandwidth for a Waveform analyzer, and suitably multiplied, divided, spread, or compressed for other methods of signal analyses and study. This invention concerns `a method and apparatus for accomplishing these functions.

An object of this invention is to repeatedly scan `at a selected rate a record track on a selected `fragment of a record continuously for la plurality of successive, end-toice end contiguous, non-overlapping scans Without dissociating the fragment from the remainder of the record and which record track does not necessarily close upon itself for the purpose of enabling the signal recorded on said track to be examined and analyzed.

A further object is to provide an improved method and means of frequency multiplication, frequency division of a recorded signal, expansion or `compression of a signal recorded on a record, examination and searching scrutiny of very short time intervals of'an analogue signal, however complex, and examination of sinusoidal or continuously variable or complexer pulsed signals for subtle variations.

A further object is to provide an improved research tool for use in the study of magnetic recording tape and magnetic recording wire properties and magnetic head performance characteristics.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 illustrates in cross-section an embodiment of a magnetic rotatin-g head scan assembly in accordance with this invention,

FIG. 2 is an end view of FIG. 1 taken from the righthand end with the end cap removed and cutting across shaft section 112 and minus the magnetic heads,

FIG. 2a is a side view of the structure in FIG. 2,

FIG. 3 heads in place,

FIG. 4 is a view taken along line 4-4 of FIG. 1,

FIG. 5 shows another embodiment generally similarl to that shown in FIG. l differing primarily in that in FIG. 1 the sensing tips of the magnetic heads terminate and form part of a continuous ring-like surface Whereas in FIG. 5 the sensing tips of the magnetic heads are notl limiting since the invention applies to the other conven' tional record types mentioned previously.

In its broader aspects, this invention concerns repetitively scanning the record track of any selected fraction or segment of a record medium with a suitable record sensing means by moving the record and the sensing means relative to one another so that the record track section of interest is sensed at every instant in one narrow local zone which moves from one end of the record track to the other end of the record track and coincidentally with the local zone leaving the record track at its other end, the local zone reappears at the one end of the track, the scanning action repeating for a plurality of successive scans enabling scrutiny, analysis and study of Vthe waveform. The moving localzone is as narrow as possible, within practical limits, so that overlap of the played'back ends of a record track is negligible. In the case of magnetic tape or magnetic Wire, several inches of the record track can be readily played back for continuous display on an oscilloscope or for feeding the signal to a waveform analyzer. T he length of 'track that can be continuously scanned in this manner is limited by practical considerations, such as the length of waveform that can be reasonably and clearly displayed on an oscilloscope, rne-` is a view like FIG. 2. but with the magnetic` atany `'ome time,` as one sensing tip passes out of sensing engagement at o'neend ofthe record track asucceeding sensing tip passes into sensing engagement at the other end of'th'erecr'd trckl The rotating magnetic scan head 100 shown in FIGS. 1-4v includes a central integral rotary member 102 of nonmagnetic material such as nonmagnetic stainless steel, that Vis Yturned down with high accuracy from a piece of stock about an axis defined by centers-10241 and 102i?. Accuracy is important because eccentricityin the rotating scan head can distort a played back signal. Nonmagnetic material is important so' as'` not to contribute to saturation of the magnetic headscarried thereon as described below. The rotary member. 102 has an end section 104lof comparatively small diameter, a second section '106 of largerY diameter adjacent theretofandabout twice aslong as section 102, a spacingshonlder 109. adjacentsectio l106, a fourth section 110{.(EIG. 2). adjacent shoulder. 109. and of considerablyflarger.diameter,` a short fifth section 1,12 adjacent to section 110, and a sixth; section'114.- that is. of slightly smllerdiainetrthan the adjacent fth section. 1112. "The Sectionill Qfvtherota'rymember. is threaded at its free.

end 116 and one end 118 of the second section 106 is.'

threaded., Twoldiametrically opposedslots 120a and'120b examined. longitudinallyjin the vsecond-section 106 and extend from` thethreaded portion 118 to spacing shoulder..

spectively. The dimensions of the slots 120.1and'holes,

122 andgthe angle at which. the holes 122.,.are drilled are .QITICQL SiIlCQ. hyerye. Only as channels. for insulated electricwires. lhesection, 1101s .formed with a peripheral misst opposite` portions of; fourtht section4 110... are. formed. with. rssassss. and 12J-tb (Elo. a). non holes. 126@ and. 1261 are driued throughl thc-...section 11,0. at thebonpmor the recesses-1 A; Sleeve. 1.40.i.s. Secured. onthe sectionlo inabunnent with. 'pasins. Shoulder. 1.0.9... Onemethod of seeurinshe sleeve without introducing anyunbalance. in the rotary msmbn 1.9.2 isfahriate .the Sleeve sothat itsinsdediametei' is the same as the otitside, diameter. o@ section. 106,` freeze. the '.rstsryfmsmbss 1.122.7 to. cause. it. toconrractand Sli'th slsereover. the sation. 1.0.6. When. the rotary sec engagementwiththe, sleeved-40. With `the sleeve 140 scredmtliefeon, .tli'e'rtary', member. 102 is carefully finish ed off, Soltht. eei/.el 14.0,n sections A10.4`and 11.4,'and

lllgflz (FIGS. 2, ,2a. andi). Diametrically,

1.0.2 fstvrftsassm.temperaturen expandsimo;

theftwo 'mag'n C heads'. whose electricalY chal?.

mosetting plastic iills the gap between the pole tips and ring 123v rendering the peripheral cylindrical surface of ring 123 continuous. This step may be carried out by wrapping tape around the ring 123 as a mold, then adding the ller material. After the tape is removed, the peripheral surface of the filler is polished so as to be smooth and continuous with ring 123 and the sensing tips ofthe magnetic heads. The two magnetic heads are connected in series.

Many commercialV magnetic heads have opposed p ole tips, eg., the magnetic heads'shown in FIGS. 5 and 6. However, it has been found that as a practical matter, one sensing head with two sensing tips` cannot be used because the surfaces of the sensing tips are not as far from the center of the head asl other portions of commercial sensing heads. If not for this limitation, one sensing head could be used.

A first tape edge guide 148 ismounted for free rotation on the section 114 of rotary member '102; Two dimensions of the tape edge guide 148- that must be very precise are the, outside diameter of the lip 150 which must be equal to the outside diamter of ring 123,r and the bore 152. which must seat bearings; the 'outside surface of the'lip 150.and inside surface of the bore 15,2 must be coaxialy with the axis of rotary member 102. The tape guide 148 mustbe nonmagnetic so that as the magnetic heads142afand-1f42b move relative tothe tape guide 1,48 there yisnosignal induced by the tape guide'. Also, because` the tape guide 148I is to be as free running as possible on the rotary member 102 so as to present minimum frictional. impedance to magnetic tape that it guides, it, ismade of lightweight material such as aluminum and is recessed as much.. as possible. To assemble the tape guide148 on the rotary member 102, rst the guide 148 is positioned over. the section 114. Then spacer sleeve 15.4, ball. bearing 156, spacer 158-, ballbearing 160 are slippedonto the section 114A in sequence. A dished retaining. ring 162 is. disposed in groove 164 of the tape guide. 148 and. understress engages the ballfbearing 160 so; that. the. inside. lip4 166 of Vthe tape guide 148 bears firmly. against. the outer race of ball bearing 156. A spacer, 168. thenfis slipped. onto section 114 under retaining. ring 168,' being smallenough not to interfere therewith, and an acorn nutv to provide a smooth free end to the rotary member engages threaded portion 116. The length of; spacer154is. such that lip 150ofthe tape guide 14,8is close .to ringl23 offsection 110.

A second tapeV edge guide 172 similar in design and functionI to, tape edge guide 148 vand likewise non-inagneticis assembled on the Sleeve v from the other` end` ofrotary member 102 for,freerotationthereon The outside diameter of'lip174must equal the outside diameter of ringl 1123.; the bore 17.6. must. registerwith the outer.-

races of'Y ballv bearings. The outside. surface of lip 174 and the inside surface.. of the. bore 176 must be coaxial with the axisoffrotary member 102. To assemble the tapeY guide` 1,172;y onthe rotarymember 102, iirstv the guide 172, is positioned over. therotary member 102. Then bearing-1,78.; sp'aerl, andA ball hearing182 are slipped onto'the sleeve 140` in sequence and within the confines` offthe tape edge guide 172.v A dished retaining ring 189 washer 196, and an insulating washer 198. An insulating sleeve 288 and a slip ring 222 concentric therewith follow the washer 198; they are filed at one end to provide a radial notch, not shown for seating a conductor. A short length of fine insulated wire 284 is soldered at one end to the notched portion of slip ring 282 and nested in the notches of the slip ring 282 and the insulating sleeve 288, and then the insulating sleeve 200 andl slip ring 282 are slipped onto rotary member 102 together and at the same time the insulated wire Ztl-tl is threaded through the slot 12de in section 106 and the hole 122a in section 118 the sleeve and slip ring abuts the insulating washer 198; the free end of wire 2M projects out of hole 12251 and is electrically joined to the magnetic head 142e.

An insulating spacing collar 286 then is slipped onto rotary member 182. An insulating sleeve 288 and a slip ring 210 concentric therewith follow the collar 286; they are led at one end to provide a radial notch no-t shown for seating a conductor. A short length of ne insulated wire 212 is soldered at one end to the notched portion of the slip ring 216 and is nested in the notches in both' the slip ring 218 and the insulating ring 288 and then together are slipped onto the rotary member 102 as the wire 212 is threaded through the slot 120b in section 186 and the hole 12219 in section 11() until the sleeve and slip ring abut the insulating collar 286; the free end of the wire 212 projects out of hole 12212 and is electrically joined to magnetic head 1Mb. An insulating washer 214, a metal washer 216, and a jam nut 218 engaged with threaded portion 118 of section 186 secure the slip ring assembly on the rotary member 102. The wipers for the slip rings are supported on a mounting member 228 for the rotatable assembly.

The mounting member 220 lis formed with a flange 222 having bolt holes 22d, integral with a cup-like section 226 from Which extends longitudinally a pair of parallel arms 228 terminating in an integral ring 230. The inside diameter 232 of the ring 238 and the inside diameter of the bore through the bottom of the cup-like section 226 must be coaxial. A ball bearing 234 is mounted in ring 238. Then the mounting means 228 and the rotatable assembly are assembled end wise. A collar and set screw 236 secures the mounting means 228 and the rotatable assembly together.

Paired wipers 240 (FlG. 4), secured to the ends of two U-shaped spring members 242, one for each slip ring are provided for engagement with the slip rings 282 and 210. The engaging surfaces of the wipers and slip rings must be smooth to minimize the noise level introduced intov the signal by this assembly. The signal-to-noise ratio can be improved by incorporating a transistorized preamplifier in the scan head assembly to lessen the eiect of noise introduced at the wiper contacts. Also, the wipers must be nonmagnetic, or as little as possible, so as not to induce pulses in the magnetic heads during each revolution of the rotatable assembly. An insulating support 246 for one of the U-shaped springs 242 is secured to one of the arms 228, and an insulating support 248 for the other of the U-haped springs 242 is secured to the other arm 228. A cover is secured to the ring 238. The metal cover 250 is slotted endwise at 252 and 254 to provide passageways for electrical connections (FlG. 4) to an oscilloscope, waveform analyzing equipment, or the like, not shown.

FIG. 7 illustrates a tape feed arrangement for the rotating head assembly described above. The unit 180 is mounted on a panel 276. A tiywheel 272 is secured to the rotatable part of the assembly to minimize wow during scanning. A pair of magnetic slugs are secured to the flywheel in line with the sensing tips, not shown in FIG. 7, and a magnetic impulse unit is supported adjacent the periphery of the flywheel for generating a pulse for counting or for synchronizing the sweep on an oscilloscope. The flywheel is friction driven by a rubber wheel 274 on the shaft of a drive motor, not shown. An idler 275 is mounted on the panel 270 adjacent the unit 100. A second idler 276 is mounted adjacent the unit and is adjustable so that record tape engaging the unit 100 and idlers 27S and 276 engages the unit arcuately for precisely 180 degrees. The adjustable mounting for idler 276 includes an oblong flat member 277 to which is secured a stud 278 supporting asleeve 280. The idler 276 is mounted for free rotation on the end of the stud 278 remote from member 276. The panel 270 is formed with an oblong hole 282 whose width is substantially the same as the outside diameter of sleeve 280 and the sleeve is disposed in registration with the hole 282. Beyond the ends of the oblong hole 282, the panel is formed with two more oblong holes 284, 286 through which pass screws 288 for adjustably securing the oblong member 277 to the panel 278. Beyond the hole 286, the panel is formed with another oblong hole 298 transverse to the others, and alongside the hole 296 is secured a bearing member 292 for a thumbscrew 294 whose head extends transversely through the hole 290 and whose other end is threadedly engaged with the member 277. A snap ring 296 retains the thumbscrew 294 in position in the bearing 292.

To adjust the idler 276, magnetic tape having a simple waveform signal recorded thereon is disposed in engagement with unit 188 and idlers 275 and 276, with the tape held stationary and under tension. The unit 100 is electrically connected to the vertical deflection means of an oscilloscope. The above-mentioned sine pulse generator is connected to the horizontal sweep circuit and then the rotatable member is driven at a constant speed. The horizontal sweep is adjusted so that there are two scans for every rotation of the member 182. With the screws 288 loosened, the thumbscrew is rotated to micrometrically adjust the wrap to 180 degrees. If the wrap is less than 180 degrees, a notch appears in the signal envelope at the scan rate. As the wrap is increased to more than 180 degrees, a peak is superposed on the signal envelope at intervals equal to the scan rate. This adjustment becomes critical at short wavelengths and phase `distortion is introduced if each sensing tip does not engage the tape in identical phase relationship to any sine wave signal recorded on the tape. With random analog data, this is less important. If the arcuate engagement is less than 180 degrees, less than maximum utility is achieved. The screen persistence of the oscilloscope selected for this purpose must be proper for the order of the scanning speed of the rotating head assembly.

There is also secured on the panel 270, an idler 300, a conventional stationary magnetic head 302, tape drive capstan 384 and rubber idler 386 for insuring good frictional engagement between the tape and the capstan. The drive for the capstan must be controllably variable for a variety of speeds from zero upward. A springloaded tape compliance arm 388 is mounted on the panel beyond idler 272. An erase head is omitted for clarity. Additional tape stabilizing rollers and a flywheel load for at least one of the idlers can be added to further insure smooth and straight tape travel over the heads. To rapidly monitor a tape to check for anything of interest, the kmagnetic head 382 may be used to play back the recorded signal and the unit 100 may be bypassed by the tape. If there is anything of interest on the tape, the section or sections of interest of the tape are disposed in engagement with the unit 180 to enable detailed examination of the recorded signal.

The modification of the rotating scan head assembly shown in FIG. 5 differs from that shown in FIG. l primarily in that the magnetic head sensing tips of the assembly shown in FlG. 5 are not part of a ring such as 123 (FlGS. 2a and 3) and in the assembly 4shown in FIG. 1 whereby the tape is supported only along its edges. Though the magnetic sensing heads shown here are different frornthose shown in 1 there is no significance inthe difference but is merely illustrative, of variety avail-- able in the commercial; market. Also because there isy noring 123, the magnetic sensing heads are supported by a circular flange instead o a recessed relatively massive section'as section 110 in FIIG. 1. In this` assembly, the` recorded surface of the tape is subjected .to the wiping action of the sensingrtips only rather thanY by a continu,

ousl ring -as 123 in FIG. 1. This arrangement is advan.

tageous as faras tape wear is concerned. Since each sensing tip, should emphatically push against Ithe surface o fthe tape as it engages and leaves thel latter during ro., tation, the sensing tips should protrude radially beyond. the .tape support surfaceon the order lof .005v inch. However, it was found that a pronounced transient and related harmonics are generated as a result of each sensing tip whipping the tape namely each 180 degrees revolution of the rotatable unit. In the embodiment shown in FIG; l, there is some advantage 'in havingthe sensingv tips pro-v trude radially beyond the tape support surface up tov about inch but the transient generated. because` of it is substantially. negligible. The friction` between tape andthe rotatable unitinFlG..1 is` far greater than tape andthe rotatable unit inv FIG. 5. When it is necessary to scan continuously a selected fragment of tape at high speed for fiiiteen minutes or more, the oxide. coating on some tapes becomes heated: and deteriorates accompaniedV by reduction of signal'. This lossis even more pronouncedA where .the data on the tape is characterized by ne grain spetztrurn.` In using the embodiment `of FIG. 5 it was foundthat atape fragment could be scanned for several hours with. Ilittle reduction in signal vleaving only -a pol ishedeifect apparent on the oxide surface.

'lhe modification shown in FIG.v 6 differs from. that shown in FIG. 1 inithat it doesnot include freely rotatable endcaps 148jas inKFIG, l for guiding the tape past the. magnetic sensing heads` but instead includes tape guide. means that is immovable relativetothe magnetic sensing heads andwheren the sensing 'tips form part of a continuous ring surface as in the embodiment of FIG. l'. The prime advantage of this structural arrangement over those inlIGSA 14 and; 5` is that the tape guides, in not moving,4 relative to the. sensing heads, cannot possiblyinduce anysignal in the.k sensing, heads. However, this structure has. the. disadvantage, causing wear at even a. faster ratethan the structure oftFIG. 1;.

The inlluence oli minuterandom magnetic iields. isl considerable when the scanning heads are operated at high speed-1becauseL even. the slightest field can cause an appreciable magnetic. pulsev of i amplitude suliicient` to maskin. part or. even entirely the signal of interest. Itisbest to. demagnetize. allv possibly susceptible materiall near the scan, heads before high speed operation.

It-wasobservedy during1 use of the rotating scan headsthat `for.- any signal. scanned, peak response-'is obtained when the, ratio. of scan speed yto frequency observed by thescan. head is. identicalA -towthe ratio of vtape velocity and frequencyestabli'shed ywhen. the signal wasoriginally recorded.y

l'lhel equipment described can receive tape directly fromA a recording headfand while in motion, can scan the"` tape atevariousspeeds.y However, it h as been found that greater utility is realizedwhere the tape isv advanced until a desirable section ofrecorded materialis located'and then thetapeis stopped and the' scan assembly operated. This pe'rmitsexamination'ofa single pulse by repeating it over and over atsucha rate :that a very narrow bandV spectrum analysis can be performed, Scan' speed must not be increased: beyond that velocity Where wavelengths approach the. gap size oli thesensing tips, else discriminating'factors are introduced. The equipment has been successfully utilized.' for signal requency multiplication and division, First, by reproducing sbsonic energy atvelocities greater has "the, fessiers velada the signal. frequency. 'rense- 8 is multiplied to a Ibandwidth over which high speed analyzers may function, properly compensated for the related frequency multiplication. Second by reproducing supersonic energy at velocities lower than recording velocity the signal frequency range is divided down t0 a bandwidth convenient for study.

Obviously many modifications and variations of the fpresent invention are possible in fthe light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. A rotatable magnetic scan head assembly for use in repetitively scanning a selected segment of an elongate iiexible magnetic record medium comprising a plurality of magnetic pickup heads that have substantially identi cal electrical characteristics and that have record sensing pole tips whose face areas are substantially identical and are of minimal width in the scan direction, a member supported for rotation about an axis therethrough, said magnetic heads being secured on said rotatable member with said pole tips radial with respect to said axis and the centers of the faces of said pole tips being in a common plane normal to said axis and the centers of said jpole tips` of said magnetic heads being arcuately spaced apart; about said axis by an angle equal to 360 degrees divided by the number of said magnetic heads and the faces, of said pole tips `being equidistant from said axis, means on said rotational member for supportingv a segs- :ment of said magnetic mediuml in an arcuate configuration for an arcuate distance equal to 360 degrees divided by the number of magnetic heads contiguous with the circular path of the faces of -said pole, tips about said axis for magnetic scanning by said pole. tips, said means on said rotational member for supporting a segment of magnetic medium in an arcuate configurationincluding a ring.- like member on each side of the circular path of the pole tips, said' ring-like members being supported concentric with said axis for rotation aboutsaid axis together with said rotational member whereby when said pole tips are driven in their circular path there is no spurious magnetic pickup from elements on said assembly immediately adjacent said magnetic heads because there is no relative movement between said magnetic heads and elements on said assembly immediately adjacent thereto, and electrical means on said rotational member for delivering electrical signals from said magnetic heads to utilization circuitry, Iwhereby when a segment ofan elongate magnetic record medium is supported in arcuate configuration contiguous with an arcuate portion of the circular' path of said pole tips for an arcuate distance equal to 360 degrees divided by the number of magnetic, heads, and said rotatable member is rotated, said pole tips scan .the segment of the elongate magnetic record medium in succession with substantially noVV gap or overlap between successive scans byv successive pickup heads and any signal on that 'segment is delivered by,v said*- electrical means at a repetition rate which is equal `to the rotational rate of said mem: ber multiplied by the number of said magnetic heads f whereby-a signal recorded on that segment of the record medium may be reproduced for an interval long enough for detailed analysis. 'i v 2,. A rotatable magnetic scan head assembly for` usev in repetitively scanning a selected segment of anr elongate flexible magnetic record medium comprising a plurality of magnetic pickupv heads that have substantially identical electrical characteristics vand that have record sensing pole tips whose face areas are substantially.identicaland are of minimal width in the scan direction, a, member supported for rotation about an axis therethrough, said magnetic heads being secured` on said rotatable member withV said pole tips, radial with respect tofsaid axis and the centers of thefaces of said polev tipsl being in' a'comf` mon plane normalfto said axis'andl thel centersl of. said pole tips of said magnetic heads being arcuately spaced apart about said axis by an angle equal to 360 degrees divided by the number of said magnetic heads and the faces of said pole tips being equidistant from said axis, means for supporting a segment of said magnetic medium in an arcuate coniiguration for an arcuate distance equal to 360 degrees divided by the number of magnetic heads contiguous with the circular path of the faces of said pole tips about said axis for magnetic scanning by said pole tips, said means for supporting a segment of magnetic medium in an arcuate configuration including a ring-like member on each side of the circular path of the pole tips, said ring-like members being supported on said rotational member concentric with said axis for free rotation relative to said rotational member to minimize frictional wear of the magnetic medium during scanning thereof by said magnetic heads, and electrical means on said rotational member -for delivering electrical signals from said magnetic heads to utilization circuitry, whereby when a segment of an elongate magnetic record medium is supported in arcuate configuration contiguous with an arcuate portion of the circular path of said pole tips for an arcuate distance equal to 360 degrees divided by the number of magnetic heads, and said rotatable member is rotated, said pole tips scan the segment of the elongate magnetic record medium in succession with substantially no gap or overlap between successive scans by successive pickup heads and any signal on that segment is delivered by said electrical means at a repetition rate which is equal to the rotational rate of said member multiplied by the number of said magnetic heads whereby a signal recorded on that segment of the record medium may be reproduced for an interval long enough for detailed analysis.

3. A magnetic scan head assembly for use in continuously repetitively scanning a selected record track segment that does not close upon itself and that is on a fraction of a magnetic record medium comprising: a plurality of magnetic pickup heads that have substantially identical electrical characteristics and that each have a pole tip with a record sensing scanning face, said scanning faces being substantially identical in minimal width in the scan direction, means for relatively moving said fraction and said heads in succession so that said scanning faces successively traverse said segment in sensing relation thereto with one of said scanning faces passing from sensing relation with respect to said segment at one end thereof as the successive scanning face passes into sensing relation to said segment at the other end thereof, means for adjusting the magnetic record medium relative to the pickup heads so that there is substantially no gap or overlap between successive scans by the pickup heads, and means for continuously delivering electrical signals developed in said heads.

4. A record pickup means for use in continuously repetitively scanning a fraction of a record medium along a record path thereof which does not close upon itself which comprises: sensing means including a plurality of record sensing tips whose scanning face areas are substantially identical in minimum width in the scan direction, means for moving said record sensing itps in succession along a selected path with one only of said tips along said selected path at every instant, such that when one of said tips is at one end of said path a successive one of said tips is at the other end of said path, means for supporting said fraction of said record medium contiguous with said path, means for adjusting the magnetic record medium relative to the pickup heads so that there is substantially no gap or overlap between successive scans by the pickup heads, and means for collecting any signal sensed by said tips for use in utilization circuitry, whereby when said fraction of said record medium is supported contiguous and coextensive with said path and said tips are moved successively along said path and relative to said fraction of said record medium, information recorded on said fraction of said record medium is sensed by said sensing means and is collected by said collecting means.

References Cited in the ile of this patent UNITED STATES PATENTS 2,170,751 Gabrilovitch Aug. 22, 1939 2,352,023 Schiller June 20, 1944 2,528,699 Masterson Nov. 7, 1950 2,539,837 Howell June 30, 1951 2,611,828 Gunby Sept. 23, 1952 2,647,168 Rivas July 28, 1953 2,737,646 Muiiiy Mar. 6, 1956 2,773,120 Masterson Dec. 4, 1956 2,794,066 Mullin May 28, 1957 2,832,840 Morin Apr. 29, 1958 2,903,521 Ellison Sept. 8, 1959 

1. A ROTATABLE MAGNETIC SCAN HEAD ASSEMBLY FOR USE IN REPETITIVELY SCANNING A SELECTED SEGMENT OF AN ELONGATE FLEXIBLE MAGNETIC RECORD MEDIUM COMPRISING A PLURALITY OF MAGNETIC PICKUP HEADS THAT HAVE SUBSTANTIALLY IDENTICAL ELECTRICAL CHARACTERISTICS AND THAT HAVE RECORD SENSING POLE TIPS WHOSE FACE AREAS ARE SUBSTANTIALLY IDENTICAL AND ARE OF MINIMAL WIDTH IN THE SCAN DIRECTION, A MEMBER SUPPORTED FOR ROTATION ABOUT AN AXIS THERETHROUGH, SAID MAGNETIC HEADS BEING SECURED ON SAID ROTATABLE MEMBER WITH SAID POLE TIPS RADIAL WITH RESPECT TO SAID AXIS AND THE CENTERS OF THE FACES OF SAID POLE TIPS BEING IN A COMMON PLANE NORMAL TO SAID AXIS AND THE CENTERS OF SAID POLE TIPS OF SAID MAGNETIC HEADS BEING ARCUATELY SPACED APART ABOUT SAID AXIS BY AN ANGLE EQUAL TO 360 DEGREES DIVIDED BY THE NUMBER OF SAID MAGNETIC HEADS AND THE FACES OF SAID POLE TIPS BEING EQUIDISTANT FROM SAID AXIS, MEANS ON SAID ROTATIONAL MEMBER FOR SUPPORTING A SEGMENT OF SAID MAGNETIC MEDIUM IN AN ARCUATE CONFIGURATION FOR AN ARCUATE DISTANCE EQUAL TO 360 DEGREES DIVIDED BY THE NUMBER OF MAGNETIC HEADS CONTIGUOUS WITH THE CIRCULAR PATH OF THE FACES OF SAID POLE TIPS ABOUT SAID AXIS FOR MAGNETIC SCANNING BY SAID POLE TIPS, SAID MEANS ON SAID ROTATIONAL MEMBER FOR SUPPORTING A SEGMENT OF MAGNETIC MEDIUM IN AN ARCUATE CONFIGURATION INCLUDING A RINGLIKE MEMBER ON EACH SIDE OF THE CIRCULAR PATH OF THE POLE TIPS, SAID RING-LIKE MEMBERS BEING SUPPORTED CONCENTRIC WITH SAID AXIS FOR ROTATION ABOUT SAID AXIS TOGETHER WITH SAID ROTATIONAL MEMBER WHEREBY WHEN SAID POLE TIPS ARE DRIVEN IN THEIR CIRCULAR PATH THERE IS NO SUPURIOUS MAGNETIC PICKUP FROM ELEMENTS ON SAID ASSEMBLY IMMEDIATELY ADJACENT SAID MAGNETIC HEADS BECAUSE THERE IS NO RELATIVE MOVEMENT BETWEEN SAID MAGNETIC HEADS AND ELEMENTS ON SAID ASSEMBLY IMMEDIATELY ADJACENT THERETO, AND ELECTRICAL MEANS ON SAID ROTATIONAL MEMBER FOR DELIVERING ELECTRICAL SIGNALS FROM SAID MAGNETIC HEADS TO UTILIZATION CIRCUITRY, WHEREBY WHEN A SEGMENT OF AN ELONGATE MAGNETIC RECORD MEDIUM IS SUPPORTED IN ARCUATE CONFIGURATION CONTIGUOUS WITH AN ARCUATE PORTION OF THE CIRCULAR PATH OF SAID POLE TIPS FOR AN ARCUATE DISTANCE EQUAL TO 360 DEGREES DIVIDED BY THE NUMBER OF MAGNETIC HEADS, AND SAID ROTATABLE MEMBER IS ROTATED, SAID POLE TIPS SCAN THE SEGMENT OF THE ELONGATE MAGNETIC RECORD MEDIUM IN SUCCESSION WITH SUBSTANTIALLY NO GAP OR OVERLAP BETWEEN SUCCESSIVE SCANS BY SUCCESSIVE PICKUP HEADS AND ANY SIGNAL ON THAT SEGMENT IS DELIVERED BY SAID ELECTRICAL MEANS AT A REPETITION RATE WHICH IS EQUAL TO THE ROTATIONAL RATE OF SAID MEMBER MULTIPLIED BY THE NUMBER OF SAID MAGNETIC HEADS WHEREBY A SIGNAL RECORDED ON THAT SEGMENT OF THE RECORD MEDIUM MAY BE REPRODUCED FOR AN INTERVAL LONG ENOUGH FOR DETAILED ANALYSIS. 